History of Life on Earth Flashcards
give 4 examples of INDIRECT methods to date fossils & rocks
- Relative Dating
Layers; any rock layer below this one is older -> judge ages relative to each other - Paleomagnetic Dating
Particles of rock orientate towards earth’s poles ; tempo @ which magnetic poles of earth change & compare it with orientation of particles - Fauna Comparisons
fossils are found in & between layers of volcanic rock that can be dated - Dendrochronological Comparisons
trees annual rings -> age & climate
Name a direct method to date rocks and fossils and explain in full
RADIOMETRIC DATING
- rocks contain radioactive isotopes -> uranium ; thorium ; potassium
- these isotopes decay at a constant rate
- age can be determined by: studying ratio of radioactive isotopes & their stable forms ; uranium decays to lead
- different isotopes date different rocks & materials ; mineral contents & type of fossils determine the method used
- radiometric dating measures in millions of years
- radiometric dating methods are constantly refined to get more accurate
From the Earth’s history what is a hypothesis for how life on earth began?
Life probs started as an organic molecule with the ability to replicate itself ; the molecule most likely used is RNA for this replication
what was the most primitive form of life on earth & where can they be found?
- a group of bacteria : Archaea / Archaeabacteria
- From hot water sources in volcanic areas / warm water spouts in the deep sea / marshy areas with little or mo oxygen or water in high salinity
where do scientists think the earliest form of life originated from?
warm water spouts under the sea
what was the group called after archaea and why were they important?
eubacteria ; first photosynthetic organisms as well as process of denitrification and fixation of nitrogen
why was the development of the cyan bacteria so important? explain in full detail
• cyan bacteria have off oxygen as a waste product of photosynthesis so:
- life could exist anywhere on earth
- light energy was used
- only ground substance was need were water & carbon dioxide -> available in abundance
- oxygen was produced
how does the atmosphere adapt to make life suitable? (5)
- photosynthesizing bacteria take in C02 and release 02
- concentration of C02 decreased as photosynthesizing organisms increased
- nitrogen levels increase ; cyan bacteria used N2 in water to produce proteins
- Atmospheric pressure decreased
- development of the ozone ; increased O2 & increase exposure to ultraviolet
why was there never a balance between CO2 and O2
- not all dead organisms decompose
- some were buried under layers of sediment to later turn into fossils
- CO2 in seawater bound with calcium to from calcium carbonate -> calcium came from erosion of rocks
discuss how potentially eukaryotes were formed
archaebacteria hijacked the eubacteria
aerobic purple bacteria became the mitochondria
discuss the potential origin of chloroplasts
endosymbiosis between unicellular organisms with mitochondria & photosynthetic cyan bacteria
what is the cambric explosion?
when there was an abundance of fossils between 500-600 mya
what are fossils?
remains of organisms that lived previously and were conserved especially in sedimentary rocks and
how are fossils formed? explain in absolute full detail
- organism dies & can be converted in sediment ( bottom of sea/river )
- anaerobic conditions -> decomposition is possible
- covering with sediment ; must be fast & happens bottom of sea,river/ lake
- hard parts can be replaced by minerals
or - dissolve & only leave an impression of natural form
or - impression can be filled with minerals leaving a mould
or - whole organisms can be kept intact -> resin
what types of fossils can be found?
- Body fossils -> skeletons/bones
- Form fossils -> sediment gardens around organism but organism is dissolved by acid water
- Moulds -> cavity filled with minerals
- Trace fossils -> marks made by animals as it walked over sediment that hardened
- Unchanged fossils -> insects in resin / frozen fossils ; mummified in dry temps
what percentage of organisms became fossils?
0.1%
name an example of a transition fossil and why it’s so important
Archaeopteryx
exhibits fine reptilian as well as avian features
why are fossils so important? what can we deduce from them?
- trends in biodiversity
- evolutionary relationships
- forming of sediments & enabling us to understand environmental changes
- explore for economically important minerals
how is coal formed?
- often happens in marshy areas ; layer of organic material turns into peat
- rivers flood and peat is covered with sand ( sediment )
- slowly subjected to higher pressures
- all oxygen & hydrogen disappear from layers and carbon increases then peat turns into coal
what were the transition animals for mammal-like reptiles called?
terapsids
why do 99,9% of species go extinct?
name 5 reasons
- couldn’t adapt to changing climate
- didn’t have time to adapt
- other species developed into new species
- new species were better competitions and existing species couldn’t survive
- killed by whatever causes extinction e.g. meteorite
define extinction
massive number of species all over the world die simultaneously
what is the sixth extinction and how is it different from other extinctions?
Also what caused it
- the damage done by man
- caused by man & much faster
- result of exploitation of natural resources, habitat destruction and pollution
name 3 intrinsic factors that caused mass extinction on earth
- volcanic eruptions
- continental drift
- ice ages
